Intestinal epithelial cell regulation of macrophage and lymphocyte interleukin 10 expression
L. M. Napolitano, M. M. Buzdon, H. J. Shi and B. L. Bass
Department of Surgery, Baltimore Veterans Affairs Medical Center, University of Maryland School of Medicine, 21201, USA. LNapolitano@surgery2.ab.umd.edu
BACKGROUND: The intestinal mucosa is subject to daily antigenic challenge
and to injury by proinflammatory cytokines. Interleukin 10 (IL-10) is an
important anti-inflammatory cytokine produced by macrophages and
lymphocytes that modulates this response. OBJECTIVE: To investigate the
hypothesis that intestinal epithelial cells are a significant local source
of IL-10 in the gut milieu and also participate in the regulation of
macrophage and lymphocyte IL-10 expression in the intestinal
microenvironment. METHODS: C-205 cells, a human intestinal epithelial cell
line, were cultured for 2 days; lipopolysaccharide or tumor necrosis factor
was then added. Media and cells were harvested at specific time points to
determine the kinetics of IL-10 expression. C-205 cells were then
cocultured with macrophages or lymphocytes isolated from human peripheral
blood mononuclear cells, and IL-10 expression was assessed in unstimulated
and stimulated conditions. Interleukin 10 protein was measured by
enzyme-linked immunosorbent assay; IL-10 gene expression was measured by
reverse transcriptase-polymerase chain reaction. RESULTS: Constitutive
production of IL-10 protein by C-205 cells was maximal at 3 days,
paralleled by a peak in IL-10 messenger RNA (mRNA) expression at 24 hours.
Lipopolysaccharide or tumor necrosis factor strikingly up-regulated IL-10
mRNA and protein expression by C-205 cells. Coculture of C-205 cells with
macrophages or lymphocytes significantly increased
lipopolysaccharide-stimulated IL-10 protein and mRNA release compared with
C-205 cells, macrophages, or lymphocytes cultured alone. CONCLUSIONS:
Enterocytes are a responsive source of IL-10 and may play a role in
modulating production of this important cytokine by the local inflammatory
cells of the gut. These redundant mechanisms to augment IL-10 production
suggest a central role for this cytokine in regulation of the local
intestinal inflammatory response.